Physiological responses of fresh,cut apple slices under high CO₂ and low O₂ partial pressures

The physiological responses of 'Delicious' apple slices to 0-30 kPa CO₂ at 0-10 kPa O₂ partial pressures at 5°C have been studied. Increasing CO₂ partial pressures from 0 to 30 kPa at 0.5, 1 and 10 kPa O₂ reduced respiration rates and ethylene production of the slices. The inhibitory effect of CO₂ on respiration rate of slices was best explained by an enzyme kinetics model that combined competitive and uncompetitive types of inhibition. Browning increased during storage and was reduced by CO₂ to only a limited extent. CO₂ levels of 15-30 kPa resulted in about a 50% reduction in acetaldehyde, ethanol and ethyl acetate concentrations in tissues under both anaerobic and low-O₂ atmospheres compared with slices kept in CO₂-free atmospheres. Elevated CO₂ might provide a mechanism to reduce accumulation of fermentation products but sensory quality of slices needs be studied before recommending its use.